A mobile crusher including a crusher that crushes raw material has been typically known. In such a mobile crusher, raw material conveyed by a feeder is crushed to a predetermined size by the crusher to be discharged by a discharge conveyor. It is known that a detector being adapted to detect the presence or absence of the raw material or detect the load of the raw material is provided to each of the feeder and crusher to detect that the feeder and crusher go into an idle state (which is a state where the work implement is operated without the raw material or crushed material therein), so that a controller lowers an engine speed to an idling speed (decelerated speed) in such an idle state, thereby reducing fuel consumption (Patent Literature 1). It is also known that a controller controls the injection quantity of fuel depending on the weight of raw material fed on the feeder irrespective of the presence or absence of the raw material within the crusher (Patent Literature 2).